1. Field of the Invention
The present invention relates to a radiation-shielded holder for an injector for administering a radioactive material, especially a radiopharmaceutical liquid, to a living body.
2. Description of the Prior Art
There is a syringe-type radiation-shielded injector for administering a radiopharmaceutical in medical treatment to a human body, which comprises, for example, as shown in FIG. 7, a lead cylinder 1 provided with a cutout extending on a peripheral wall in a lengthwise direction, a syringe-type cylindrical body 3 filled with a radiopharmaceutical inserted into the cylinder 1, and a transparent lead glass plate 2 fitted into the cutout so as to permit viewing the dosage scale of the inserted body 3, body 3 being held in place by pressure from a fixing screw member 4, wherein a syringe plunger (not shown) assembled to the body 3 can be operated to perform administration of the radiopharmaceutical to the patient while holding the cylinder 1 with one hand, thus protecting the operator's hand and body from radiation exposure.
However, if, in the above conventional radiation-shielded injector, the wall thickness of the cylinder 1 and the plate thickness of the glass plate 2 are adequately selected, shielding of the radiation emitted radially on the inner wall surface of the cylinder 1 and the inner surface of the glass plate 2 from the syringe-type body 3 can be sufficiently achieved as shown in alternate long and short dash lines in FIG. 7, but the radiation which transmits through the border between the cutout edge portion of the cylinder 1 and the glass plate 2 from the body 3 in the radial direction as shown in solid lines in FIG. 7 is shielded only with a thick-wall part of the wall thickness of the lead cylinder 1 and a part of the thickness of the glass plate 2, because of which considerable leakage of radiation occurs at the border part. The conventional injectors have a grave drawback in that the construction of shielding radiation cannot sufficiently protect the operator's hand and body from radiation exposure. On the other hand, it may be supposed to enlarge the diameter dimension of the lead cylinder or the thickness of the lead glass plate, but it is difficult to put such measures into practice because of the increase in the size and weight of the whole apparatus and the consequent deterioration of operating simplicity which is normally effected with one hand.